FEM Design of a Cutting-Edge Support System for Micro-GT

Abstract

The design of the support system (shaft, bearings, and mechanical coupling devices) of the rotor plays a key role in the development of efficient micro-gas turbines (micro-GTs) for distributed power generation. Foil air bearings are the most widespread technical solution well suited to design a reliable support system, although they cannot withstand a large number of start-stop cycles of the units. In order to overcome such limitation, we have recently proposed an innovative support system that takes advantage of spline couplings and two bearing types (e.g., air and rolling-element bearings). The devised support system employs splines as both convenient coupling systems and actuators for the load partition between the two bearing types. In the present work, the helical spline coupling is studied by means of structural FEM analyses including contact simulation in order to design the support system. Numerical results confirm previous findings in that the load transfer through the spline coupling is mainly a function of the helix angle. In addition, friction factor and structural stiffness cannot be neglected in the accurate design of the spline coupling. Such design parameters are now included in the proposed design procedure, which formerly assumed frictionless contact and rigid bodies.

Preliminary Design of a Mini Gas Turbine via 1D Methodology

“…The pressure rise in the compressor and its sudden decrease in the turbine causes a force imbalance between the operating machines. The relevant axial loads in usual practice are partially compensated by sending pressurized air in the backdisk sealings [44] or by means of more sophisticated technical solutions [48]. For the present application, we propose that a small extraction of the mass flow exiting from the compressor is being used for sealing and force balance.…”